Electric clock system



March 10, 1925. 1,529,331

H. E. WARREN ELECTRIC CLOCK SYSTEM Filed May 16, 1924 2 Sheets-Sheet 1 Inventor; Henrg EM/arr-en,

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March 10, 1925.

H. E. WARREN ELECTRIC CLOCK SYSTEM Filed May 16. 1924 2 Sheets-Sheet 2 Inventor: Henrg BWarr-en,

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Patented Mar. 10, 1925,

UNITED STATES 4 PATENT OFFICE.

HENRY EQWARREN, OF ASHLAND, MASSACHUSETTS, ASSIGNOR TO WARREN CLOCK COMPANY, OF ASHLAND, MASSACHUSETTS, A CORPORATION OF MAINE.

ELECTRIC CLOCK SYSTEM.

Application filed May 16, 1924. Serial No. 713,843.

T all whom it may concern:

Be it known that I, HENRr E. WVARREN,

a citizen of the United States, residing at Ashland, in the county of Middlesex, State of Massachusetts, have invented certain new and useful Improvements in Electric Clock Systems, of which the following is a specification.

- My invention relates to electric clock systems of the type Where one or more electrically operated secondary clocks are supplied from a system of distribution which is controlled in such a way that the secondary clocks will indicate time. My invention relates more in particular to the provision of means for setting the Secondary clock of such a system from a distant control station and if desired, this may be'accomplished automatically for example by means of a master clock which controls the timing function of the system. My invention is particularly applicable to clock systems which utilize the frequency of an alternating current system as the time controlling medium and in which the secondary clocks are driven by synchronous motors.

In carrying my invention into effect, I

provide the synchronous motor driven secondary clocks with more than one speed' relation between the motor and the clock hands. One speed relation is for normal operation and another speed relation is utilized to operate the clock hands at a considerably higher speed for the purpose of setting the clock. For changing from one speed relation to the other, I prefer to utilize the field of the driving motor as a voltage responsive relay in addition to its usual function. For example, for normal operation, I may impress a normal voltage upon the system and for clock setting operation, I may impress a different voltage upon the system which will operate the relay to change the speed relation between the motor and the clock hands which it drives. This --is feasible because the speed of a synchronous motor is independent of voltage changes over a considerable range of voltage, consequently, the change in voltage necessary to perform the relay function has no effect upon the speed of the motor and conversely, a change in frequency such as is desirable to make minor corrections in the time indications of the clocks has no effect upon the relay as such. Where the system is controlled b a master clock, such for example, as is escribed in my rior United States Patent 1,420,896, I pre er to utilize the master clock to automatically change the voltage of the secondary clock system m such a way as to automatically set the secondary clock correctly after a shut down of any appreciable duration such as might be caused by a failure of the alternating current supply.

The features of my invention which I believe to be novel and patentable will be pointed out in the claims appended hereto. For a better understanding of my invention, reference is made in the following description to the accompanying drawings, Fig. 1 of which is a side view of a secondary clock movement together with its circuit connections arranged according to my invention so that an increase in voltage above normal produces the clock setting function; Fig. 2 1s a sectional perspective representation of the clock movement of Fig. 1, as viewed from the rear of that figure; Fig. 3 is a side view of a secondary clock movement together with its circuit connections arranged to accomplish the clock setting function when the voltage is reduced below normal; Fig. 4 is an end view of the clock movement shown in Fig. 3; and Fig. 5 represents a complete clock system provided with a master clock for automatically controlling the frequency of the system and for automatically resetting the secondary clock after a shut down, the system being arranged to utilize secondary clocks of the typqe shown in Figs. 3 and' l.

eferring now more in particular to Figs. 1 and 2, 10 indicates a source of alternating current supply assumed to be of substantially constant voltage and frequency. 11 indicates a secondary clock motor connected to the source of supply 10 through a circuit control switch 12 and a voltage control switch 13. For the driving motor 11, I prefer to use a motor of the self-starting synchronous type such as described for example in my prior United States Patent 1,283,432. Such a motor comprises a field coil 14, a laminated field core 15, provided with shading coils 16 on its pole pieces 17 for producing a shifting field through the rotor of the motor. The rotor is preferably contained within -a casing 18 and the casing contains in -addition to the rotor, suitable reduction gearing connected between the motor rotor and the terminal shaft 19. For a detailed description of such a motor drive, reference is made to my prior United States Patent 1,456,082. Mounted upon the terminal shaft 19 of the motor is a gear wheel 20 which meshes with a gear 21 rotatably mounted upon a timing shaft 22. Connected between shaft 22 and gear 21 is a planetary or epicyclic gear arrangement comprising the parallel shaft 23 secured in gear wheel 21 near its periphery and integral gears 24 and 25 rotatably mounted on shaft 23 meshing respectively with gears 26 and 27 mounted on shaft 22. Gear 26 is secured to shaft 22 in any suitable manner such as by a set screw. Gear 27 is integral with a bushing 28 and a locking Wheel 29 provided with teeth in its periphery. The bushing 28 and the Wheels 27 and 29 carried thereby are free to turn with shaft 22 except when wheel 29 is locked by a tooth 30 mounted on the pivoted-lever 31. Between gears 26 and 27 is a friction washer 32 made of some such material as cork, paper or fibre. Gear 27 is pressed toward gear 26 by a spring 33 which is coiled about shaft 22 between a bearing plate 34 and wheel 29. The tension of spring 33 is adjusted so that the friction washer will form a driving connection between shaft 22 and planetarygear 27 when the wheel 29 is unlocked, but will allow gears 26 and 27 to slip with respect to each other when wheel 29 is locked without overburdening the driving motor. The minute hand 35 of the clock is secured to shaft 22 and the hour hand 36 is secured to a bushing 37 integral with a gear 38 rotatably mounted on shaft 22. The hour hand is driven through the usual back gear arrangement consisting of a pinion 39 secured to shaft 22 and integral gears 40 and 41 meshing respectively with pinion 39 and gear 38.

The locking lever 31 is pivoted at 42 and is normally biasedto the locking position represented in Fig. 1 by means of a counterweight 43 which is preferably adjustable. The opposite end of the lever 31 carries a soft iron armature 44 which is normally spaced away from the laminations 15 of the motor field core. The adjustment is such that a normal voltage impressed --upon the motor 11, the leakage flux from the core 15 will be insuflicient to draw the armature down against the core and hold it there. Consequently, under normal voltage conditions, the wheels 29 and 27 will be locked against rotation. When the voltage on the motor is increased for example from a normal voltage of 110 to 130 volts or more, the leakage flux will increase and draw the armature 44 to its seat on the motor core and thereby withdraw tooth 30 from locking wheel 29 and unlock wheels 29 and 27. Although it is .possible to operate this relay as described by a change in voltage as low as 15%, it is generally preferable to make the adjustment such that it requires a greater voltage change, for example, 50%,"

in order tov guard against unintentional opcrations of the relay, such as might be caused by exceptional but oftentimes unavoidable voltage fluctuations on the system.

: ne convenient way of producing the desired increase in voltage sufficient to unlock wheel 29 is by means of a transformer 45. Switch 12, which is provided for stopping the secondary clocks for any reason, is normally closed. Switch 13, provided for. setting the secondary clocks, is normally in the position shown connected in series with switch 12 and when in that position, connects the clock systemdirectly to the source 10 so that normal voltage is supplied to the secondary clocks. When switch 13 is moved to the right, the transformer 45 has its primary connected across the source 10 and the voltage of its secondary is added to the supply voltage to produce the required increase in voltage on the clock system necessary for setting the clocks.

The operation of the apparatus thus far described may be reviewed as follows: With normal voltage on the clock system, gear wheel 27 is locked and the motor 11 drives the minute hand shaft 23 through gears 20, 21, 24'and 26 at the proper rate of speed and in the proper direction tocause the clock hands to keep accurate time, assuming normal frequencybf the scource 10. The reason ,for this is that the gear 25, which is slightly larger than its integral gear 24, must under these conditions roll about the locked gear 27 in a clockwise direction at the same speed as gear 21 rotates and in so doing, is caused to rotate on its own axis in a clockwise direction. It therefore causes rotation of the integral gear 24 in a clockwise direction. If gears 24 and 25 were of the same size and gears 26 and 27 were of the same size, the movement above described would produce no rotation of gear 26. However, since gear 26 is slightly larger than gear 27 and gear 24 is slightly smaller than gear 25, gear 26 must be carried along at a slow rate of speed as compared to the speed of wheel 21 in a clockwise direction, to make upfor the difference in the gear sizes. In the meantime, the friction washer 32 allows gear 26 to slip with respect to gear 27 which is held stationary and the clock hands are driven in the proper direction and speed for normal operation.

Now, suppose it is desired to set the clock hands ahead. Switch 13 is moved to'the right to increase the voltage on the clock system so that armature 44 is pulled down and the gear 27 is unlocked. Now, since both gears-27 and 26 are free to rotate with shaft 22, the friction washer 32 holds these gears stationary with res ect to each other and the minute hand s aft 22 is driven in a clockwise direction at the same speed as gear 21 rotates, there being no rotation of gears 24 and 25 with respect to gears 26 and 27. In other words, the whole planetary system now rotates as a unit with gear 21 and the clock hands are driven at a greatly increased speed which may be made anything desired, depending upon the gear ratios used in the planetary gear. It is desirable to have a definite known speed ratio between the two conditions of operation, such as 60 to 1, in order that the operator will know just how long to hold the switch 13 closed to the right for a given advance of the clock hands without being able to see them. For example, if the clock hands rotate 60 times as fast in the setting operation as they do normally, the higher voltage should .be impressed upon the system for approximately one minute to advance the clock hands one hour. In case the clock hands are advanced a few minutes too far by the clock setting operation, the switch 12 may be opened and the clock stopped the few minutes to make the setting exactl correct.

In igs. 3 and 4, the same arrangement of planetary gears is provided and the parts which are similar to those of Figs. 1 and 2 are designated by similar reference characters, but the clock setting is performed by a reduction in voltage from normal and a slightly different arran ement of the looking mechanism is provided. In this modification, the wheel 29, which is integral with planetary gear 27, is provided with gear teeth and meshes with a pinion 46 which is integral with the locking wheel 47. The locking lever 31 is provided with an extension 48 having a lockin tooth 49 which engages with a tooth in the locking wheel 47 under normal voltage conditions. The counterweight 43 on the lever 31 is adjusted so that the armature44 is magnetically held against the motor core 15 under normal voltage conditions but is released to unlock wheel 47 when the voltage is reduced for example from 20% to 50% below normal. This is feasible because the motor 11 will still develop sufiicient torque at this reduced voltage to start'up and drive the clock mechanism at synchronous speed. It will be noted that the necessary motor torque is less during the clock setting operation than during normal operation since, in the former case, the friction washer 32 produces no load on the motor.

To reduce the voltage of the source 10, all that is necessary is to insert a resistance 50 in the circuit of the secondary clock motors which may be accomplished by opening the switch 51 which normally short circuits the resistance 50. With this arrangement, the clock hands are driven at normal speed under normal voltage conditions as before, but when the voltage is lowered by the opening of switch 5l,'the armature 44 is released, wheel 47 is unlocked andthe minute hand shaft 22 is driven at the same speed with gear 21 to advance the clock hands at a rapid rate for the purpose of setting.

I refer the modification shown in Figs. 3 an 4 because it avoids the use of a transformer", although a bucking transformer could be used, if desired, in place ofthe resistanee 50. This modification also avoids any ob ection which might be made to subectling the system to a voltage above norma In Fig. 5 I have shown, in connection with a clock system controlled by a master clock such as is described in' my former United 5 States Patent 1,420,896, automatic means for operating the clock setting relays. In this system I have represented at 60 a source of alternating current consisting in this case of a rotary converter supplied from a direct current source and supplying from its alternating current end the alternating current network 61, from which the secondary clocks are supplied through the step-down transformer 62. The speed of the rotary converter and therefore the frequency of the network 61 is controlled by the master'clock regulator in such a way as to normally maintain the integrated error in frequency at a negligible value.

The master clock regulator consists in this instance of a highly accurate master. clock represented at 63, a self-starting synchronous motor driven clock movement 11, similar to the clock movement of Figs. 3 and 4 with the exception that it drives av pulley 64 from the shaft 22 and an endless belt differential mechanism connected between the motor driven clock movement 11 and the master clock 63, together with a frequency control switch 67 and a voltage control switch 51 arranged to beoperated by the differential mechanism. The endless .belt contains a loop in which is carried the weighted pulley 65 which moves up and down as the speed of the clock movement 11 varies above or below normal. The frequency regulator 67 consists of means for varying the resistance 68 in the field circuit of the rotary converter 60 and is adjusted so that when the switch contacts at 67 are open, the speed of the rotary converter is very slightly above normal, for example, so as to produce 60% cycles when the normal frequency is 60 cycles and when these contacts are closed, some of the resistance 68 is cut out to decrease the speed to slightly below normal, for example, corresponding to 59 ,1 cycles. The movable switch lever of 67 stands in the path of a pin 70 extending raised thereby to close the switch when the pulley moves upward a suflicient distance.

The voltage regulator switch 51' has its stationary contacts connected across the resistance and its movable member has a forked lever-extending in the path of pin 70 so that as the pulley moves up past this point, the switch is closedand as the pulley moves down again, the switch is opened.

The operation of the master clock regulator is as follows: When the frequency supplied by the source is exactly correct and the voltage on the clock system is normal, the endless belt is driven at both ends by the pulleys 6i and 69 of the motor 11' and the master clock respectively at exactly the same speed. Consequently, there will be no change in the position of the differential element under these conditions and the weighted pulley will normally be in some such position as is represented in dotted lines. The switch 51 will be closed to cut out the resistance 50 and the secondary clocks on the system including the secondary clock movement 11 will have their planetary gear systems locked, as previously described, so that they will operate at substantially normal speed to indicate time. The pin on-the weighted pulley 65 will slowlymove up and down to close and open switch 67 to thereby maintain correct the average speed of the secondary clocks. I

Now, suppose the system fails, due to a shut down of the rotary converter, or the opening of the circuit breaker shown at 71, all of the secondary clocks, including the clock movement 11, will stop and the pulley 65 will descend and open switch 51 to place the resistance 50- in the circuit of the secondary clock system as represented in full lines in Fig,- 5. The pulley 65 will continue to descend until the service is again established. By this time, the secondary clocks may be'ten minutes or an hour slow, but as soon as the service is again established, the secondary clocksincluding the clock movement 11, will operate their terminal shafts at a much higher rate of speed than normal, because now, due to the decreased voltage supplied to the clock system, the planetary gear system of each such clock movement is unlocked in the manner previously described. Consequently, the clocks will rapidly be set correctly, while the pulley 65 ascends at the rapid rate of speed incident to the clock setting condition of motor movement 11' until the switch 51 is again closed to establish normal voltage on the secondary clock system. Thenithe secondary clocks and the clock movement 11' will immediately take up their normal speed a ain. It will be noted that irrespective of the uration of shut down, the differential accurately measures this duration by the distance which complishes a corresponding-advance of the clocks when the service is again established. It will be understood that without the provision of the voltage control clock setting arrangements, the secondary clocks would eventually gain in time to make up for a shut down because the frequency control devlce 67 is adjusted for maximum frequency whenever the secondary clocks are slow, but this might require hours. By the provision of the voltage control clock setting features, the secondary clocks are almost immediately reset to substantially correct time after a shut down. y

In addition to" the mechanism thus far described, I may provide another switch 72 above switch 67 controlled by the pin 70 of the pulley 65. This switch normally maintains closed the secondary clock system, but if for any reason the secondary clocks shoiild happen to get very much ahead of the master clock 63, the pulley 65 will rise and cause the opening of switch 72 and thereby cause a stoppage of all of the secondary clocks including the clock movement 11. WVith this arrangement, the master. clock 63 may be set ahead or it may be stopped by hand or by time signals and the automatic control will cause the secondary clock to closely follow the indications of the. master clock. For example, suppose it is desired to set the clock 63 ahead one hour to comply with daylight saving regulations, the pulley 69 will e arranged to move-with the clock hands (not shown) and rapidlycause the descent of pulley 65 in an amount corresponding to the advance of the master clock which operation will immediately open switch 51' and thereby cause the secondary clocks to operate at the higher rate of speed until they are advanced one hour. If it is desired to set the clocks back one hour, the master clock may either be stopped for an hour, or set ahead 11 hours; the latter will be preferable since with aratio of 60 to 1 between the normal and clock setting speeds of the secondary clocks, it will never take longer than about 12 minutes to automatically advance the clocks 12 hours.

Whenever I have used such expressions as secondary clock movement, secondary clock, or secondary timin movement in the description and claims, intend the use of the expression in a broad sense as meaning any type of timing device irrespective of whether the device-is provided with clock hands and indicates time or performs some other timing function such as the operation of a time stamp or a time switch.

In accordance with the provisions of the patent statutes, I have described the principle of operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof; but

I desire-tohave it understood that the apparatus shown and described is only illustrative and that the invention may be carried "iout by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In an electric timing system, a secondary timing movement comprising an electric motor for driving said movement, a timing shaft, a variable speed ratio driving connection between said motor and timing shaft, and means controlled by the voltage impressed upon said motor for changing the speed ratio of said driving connection.

2. In an electric timing system, a secondary timing movement comprising a self-starting synchronous motor for driving said movement, a timing shaft, a variable speed driving connection between said motor and timing shaft, and means controlled by the voltage impressed upon said motor for changing the speed ratio of said driving connection. v

3. In an electric timing system, a secondary timing movement comprising a self-starting synchronous motor for driving said movement, a timing shaft, a two speed driving connection between said motor and timing shaft, one speed connection being for the normal operation of said shaft and the other speed connection being for a higher rate of operation thereof, and means responsive to an abnormal voltage impressed upon said motor for changing the speed ratio of the driving connection from the normal rate condition to the higher rate condition.

4:. In an electric timing system, a secondary timing movement comprising a self-starting synchronous motor supplied from said system for driving said movement, a timing shaft, a two speed driving connection between said motor and shaft, one speed connection being for normal operation of said timing shaft and the other speed connection being for a'higher rate of operation, and means responsive to an abnormally low voltage impressed upon said motor for changing said connection from the normal to the high rate operating condition.

5. A secondary timing movement comprising a self-starting synchronous motor for driving said movement, a timing shaft driven thereby, means in the driving connection between said motor and shaft for changing the speed ratio thereof, and an electric relay for operating said speed changing means, said relay comprising a pivoted armature responsive tovariations in the leakage flux from said motor.

6. In a secondary timing movement, an electric motor, a timing shaft driven thereby, and means for changing the speed ratio between said motor and shaft comprising a planetary gear system connected between said motor and timing shaft, a friction washer between relatively rotatable adjacent gearsof said system so that they will otate together if unrestrained, and 'an'electrio relayfor locking and unlocking one of said ears.

' 7 11 an electric timing movement, an electric motor, a timin shaft driven thereby, and means connecte between said motor and shaft for changing the speed ratio therebetween com rising a planetary gear system havin relatively rotatable gears se arated by a riction washer so that they wil rotate together if unrestrained, and means responsive to the voltage im ressed upon said motor for locking and unlocking one of said gears. w

8. In anelectric timing movement, a selfstarting synchronous motor, a timing shaft driven thereby, and means connected between said motor and shaft for changing the speed ratio therebetween comprising a planetary gear system havin relatively rotatable gears separated by a 'ction washer so that they will rotate together if unrestrained, and means responsive to the voltage impressed upon said' motor for locking and unlocking one of said gears.

9. In an electric timing system, a secondary timing movement comprising a self-starting synchronous motor, a timing shaft driven thereby, a variable speed driving connection between said motor and shaft, and means responsive to the voltage but nonresponsive to the frequency impressed upon said motor for changing the speed ratio of said driving connection.

10. An electric clock system comprising a source of alternating current of substantially constant voltage and frequency, a secondary timing element supp-lied from said system comprising a self-starting synchronous motor, a timing shaft, a variable speed driving connection between said motor and shaft,

and means responsive to the voltage impressedupon said motor for changing the speed ratio of said driving connection, and means for changing the voltage supplied to said timing element for altering the speed ratio of said driving connection.

11. An electric clock system comprising a source of alternating current of substantially constant voltage and frequency, selfstarting synchronous motor driven secondary timing movements supplied from said system, a master clock regulator for normally maintaining the integrated error in the frequency of said system at a negligible value, and means controlled by said master clock regulator for opening the circuit of said timing system when the secondary timing movements are too fast by any substantial amount and closing said circuit again when said error is reduced to a ne ligible value as compared to the master clocfi.

12. A system for the indication of time by means of secondary-clocks comprisin a source of alternating current, self-starting synchronous motor driven secondary clock movements suppliedfrom said system, said movements having means responsive to the voltage impressed upon their motors for altering the speed at which said movements are driven by their respective motors, a master clock regulator for normally maintaining the integrated error in frequency of said altering the speed at which its movement is driven, a master clock regulator for said system, and means controlled by said regulator for altering the voltage of said clock system.

14. An electric timing system com-prising a source of current having a substantially constant-normal voltage, a timing element driven by an electric motor supplied from said system, a two speed driving connection between said motor and the timing element,

the lower speed being for normal operation and the higher speed being for setting purposes, vmeans responsive to the voltage impressed upon said system for altering said speed changing means in such a way that a normal voltage corresponds to the normal speed operating condition and an abnormal voltage corresponds to the higher speed operating-condition, automatic means associated with said system for measuring the duration of an interruption in the service, and means controlled by said automatic means for impressing upon said system after the service is again established the abnormal voltage necessary for the higher speed oper- \ation of said timing element until said timing element has been set substantially correctly and then establishing normal voltage conditions. 7

15. A clock system comprising a source of alternating current, asecondary clock movement driven by a self-starting synchronous 5 motor connected to said system arranged to drive its movement at the correct speed for indicating time when the voltage and he quency of said system is normal, means responsive to an abnormally low voltage on said system for causing said motor to drive its movement at a materially higher speed, a master clock regulator for said system, and means controlled by said regulator for decreasing the voltage condition of said system. to the abnormally low value whenever said system, means controlled by said regulater for impressing an abnormal voltage on said system when the secondary clocks indicate slow with respect to said master clock and other means controlled by said master clockfor opening the circuit of said master clock when the secondary clocks indicate fast with respect'to said master clock.

17. In an alternating current clock system, the method of operatin and setting the secondary clocks thereof, w ich consists in synchronously operating them in response to the frequencyof the system, and setting them, while maintaining synchronous operation, in responseto an abnormal voltage on the system.

18. A clock system comprising a source of alternating current normally of substantially constant voltage and frequency, one or more secondary clock movements driven by self-starting synchronous motors supplied from said source, a voltage responsive relay associated with each secondary clock movement for changing the speed relation in the driving connection between the motor and clock movement, the rela being connected to the clock system and adJusted to change the speed relation from normal to high speed relation when the voltage supplied to the system is changed from a normal to an abnormal value and vice versa, a master clock regulator for said system arranged to normally maintain the frequency supplied to said system such that the secondary clocks indicate substantially correctly with respect to the master clock of the regulator, means controlled by said regulator for establishing an abnormal voltage condition on said clock system whenever the secondary clocks become substantially slow with respect to the master clock until said secondary clocks indicate substantially correctly with respect to said master clock, and means controlled by said regulator for opening the circuit of said clock system whenever the secondary clocks become appreciably fast with respect to said master clock and closing the circuit again. after such error has been reduced to a negligible value.

19. 'A secondary clock movement comprising an electric motor, the speed of which is responsive to frequency, but non-responsive to voltage changes over a wide range of voltage, a clock movement driven thereby,

speed changing means in the driving connection between the motor and clock movement, a voltage responsive relay which is non-responsive to frequency changes over a wide range of frequency for operating said speed changing means, and a common energizing coil for both said motor and relay.

20. In an alternating current clock system the method of operating and setting the secondary clocks thereof, which consists in 10 synchronously operating them in response to the frequency of the system, and setting them, while maintaining synchronous operation, in response to an abnormally 10W voltage on the system.

In Witness whereof, I have hereunto set my hand this 9th day of May, 1924.

HENRY E. WARREN. 

